1. Field of the Invention
The present invention generally relates to a process for making phenolic ketones. More particularly, a process is provided for making phenolic ketones, which may be used as precursors to the synthesis of hydroxyaryl ketoximes, used as extractants for the recovery of metals from aqueous solutions.
2. Background of the Invention
The starting material for solvent extraction processing of copper is an aqueous leach solution obtained from a body of ore which contains a mixture of metal in addition to copper. The leaching medium dissolves salts of copper and other metals as it trickles through the ore, to provide an aqueous solution of the mixture of metal values. The metal values are usually leached with sulfuric acid medium, providing an acidic aqueous solution, but can also be leached by ammonia to provide a basic aqueous solution.
The aqueous solution is mixed in tanks with an extraction reagent which is dissolved in an organic solvent, e.g., a kerosene. The reagent includes an extractant chemical which selectively forms metal-extractant complex with the copper ions in preference to ions of other metals. The step of forming the complex is called the extraction or loading stage of the solvent extraction process.
The outlet of the mixer continuously feeds to a large settling tank, where the organic solvent (organic phase), now containing the copper-extractant complex in solution, is separated from the depleted aqueous solution (aqueous phase). This part of the process is called phase separation. Usually, the process of extraction is repeated through two or more mixer/settler stages, in order to more completely extract the desired metal.
After extraction, the depleted aqueous feedstock (raffinate) is either discharged or recirculated to the ore body for further leaching. The loaded organic phase containing the dissolved copper-extractant complex is fed to another set of mixer tanks, where it is mixed with an aqueous strip solution of concentrated sulfuric acid. The highly acid strip solution breaks apart the copper-extractant complex and permits the purified and concentrated copper to pass to the strip aqueous phase. As in the extraction process described above, the mixture is fed to another settler tank for phase separation. This process of breaking the copper-extractant complex is called the stripping stage, and the stripping operation is repeated through two or more mixer-settler stages to more completely strip the copper from the organic phase.
From the stripping settler tank, the regenerated stripped organic phase is recycled to the extraction mixers to begin extraction again, and the strip aqueous phase is customarily fed to an electrowinning tankhouse, where the copper metal values are deposited on plates by a process of electrodeposition. After electrowinning the copper values from the aqueous solution, the solution, known as spent electrolyte, is returned to the stripping mixers to begin stripping again.
While many reagent formulations have been proposed for use in recovery of copper by solvent extraction, the present invention is specifically directed to the hydroxyaryl ketoxime reagents. Hydroxyaryl ketoximes are typically derived by reacting a phenolic ketone with a hydroxylamine derivative. The most common method used for deriving the phenolic ketones is through the conversion of an alkylphenyl acetate to a phenolic ketone by way of a Fries rearrangement using aluminum chloride as the catalyst.
A significant disadvantage associated with the use of this type of process to make phenolic ketones stems from the large amounts of aluminum chloride required to make the phenolic ketones and, more particularly, the substantial amounts of aluminum chloride waste being generated thereby. Moreover, a two-pot conversion is required, i.e., preparation of the ester intermediate in one reactor, followed by transference of the ester intermediate to a second pot, i.e., second reactor, to perform the Fries rearrangement.
As was noted previously, hydroxyaryl ketoximes are derived by reacting a phenolic ketone with a hydroxylamine derivative. Thus, in order to form the desired ketoximes, another process is required, i.e., formation of the phenolic ketones in two pots, followed by transference to a third pot so that they can be reacted with the hydroxylamine derivative.